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THE BOTULINUM TOXIN

Over the past fifty years, Clostridium botulinum has become famous for its ability to produce botulinum neurotoxins. Each of the seven serotypes of this bacterium (A, B, C, D, E, F, and G) produces a unique form of protein with a high molecular weight of 150,000 daltons (also designated A through G). Botulinum toxin A is commercially available as Botox™ (Allergan, Inc) and Dysport™ (Speywood, UK). Botulinum toxin B is marketed as Myobloc™ (Elan Pharmaceuticals) in the USA and Neurobloc™ (Elan Pharmaceuticals) in Europe.

MECHANISM OF ACTION

All botulinum toxins have a similar mode of action, i.e. they interfere with the transmission of nerve impulses, inhibiting the release of acetylcholine: a neurotransmitter that transfers nerve impulses from the central to the peripheral system. The effect is long-lasting but also reversible, as new nerve endings sprout to replace previously inhibited ones.

La tossina botulinica agisce a livello della giunzione neuromuscolare (placca motrice) bloccando il rilascio e gli effetti dell´acetilcolina, responsabile della neurotrasmissione sia a livello di Sistema Nervoso Centrale (SNC), sia a livello di Sistema Nervoso Periferico (SNP). L´acetilcolina normalmente viene rilasciata nello spazio sinaptico grazie ad un potenziale d´azione che percorrendo l´assone del neurone, a livello della terminazione ultima dell´arborizzazione finale dell´assone, determina l´apertura dei canali del calcio. Gli ioni calcio penetrano all´interno del bottone sinaptico e avviano il processo di rilascio dell´acetilcolina nello spazio sinaptico dove essa agisce su dei recettori specifici (ACh-receptors), localizzati sulla membrana cellulare post-sinaptica della cellula muscolare. Interagendo con gli ACh-receptors il neurotrasmettitore realizza i suoi effetti determinando danno inizio alla contrazione muscolare. Subito dopo, l´acetilcolina viene idrolizzata dall´acetil-colinesterasi. Inibendo il rilascio dell´acetilcolina la tossina botulinica interferisce con l´impulso nervoso e determina una paralisi flaccida dei muscoli caratteristica. La tossina botulinica è, in effetti, un vero e proprio miorilassante.

Botulinum toxin acts at the neuromuscular junction (motor endplate) by blocking the release and effects of acetylcholine, responsible for neurotransmission both at the level of the Central Nervous System (CNS) and at the level of the Peripheral Nervous System (PNS). Acetylcholine is normally released into the synaptic space thanks to an action potential which, traveling along the axon of the neuron, at the level of the last termination of the final arborization of the axon, determines the opening of the calcium channels. The calcium ions penetrate inside the synaptic button and start the process of release of acetylcholine in the synaptic space where it acts on specific receptors (ACh-receptors), located on the post-synaptic cell membrane of the muscle cell. By interacting with the ACh-receptors, the neurotransmitter achieves its effects by determining the start of muscle contraction. Soon after, acetylcholine is hydrolysed by acetylcholinesterase. By inhibiting the release of acetylcholine, botulinum toxin interferes with nerve impulses and causes a characteristic flaccid paralysis of the muscles. Botulinum toxin is, in fact, a real muscle relaxant.

It is a double chain polypeptide, consisting of a heavy chain and a light chain. The heavy chain is linked to the light chain via sulfide bridges. It has been ascertained that the two chains that make up the molecular organization of botulinum toxin perform different functions. The heavy chain binds to a receptor present on the cell membrane of the synaptic button, the SV2 receptor, and initiates an invagination of the membrane itself and therefore the so-called phenomenon of endocytosis, thanks to which the botulinum toxin penetrates inside the synaptic button. Once it has penetrated the synaptic button, the botulinum toxin releases the light chain which can perform its function as a protease capable of hydrolysing the proteins of the SNARE complex (SNAP-25, syntaxin, synaptobrevin) of the neuromuscular junction, preventing the release of acetylcholine from synaptic vesicles. The proteins of the SNARE complex play, at the motor endplate level, a determining role for the release of acetylcholine because they favor the fusion between the membrane of the synaptic vesicles in which the acetylcholine is stored and the membrane of the synaptic button. The protein that is hydrolyzed is SNAP-25 and in this way the fusion between the membrane of the synaptic vesicles in which the acetylcholine is crammed and the membrane of the synaptic button is made impossible and it is for this final reason that the acetylcholine cannot be released into the synaptic space of the motor plate and the characteristic flaccid paralysis of the treated muscles is determined.

CURRENT USES OF BOTULINUM TOXIN

La BoNT-A è approvata in Italia per le seguenti indicazioni:
spasticità focale;
deformità dinamica del piede equino dovuta a spasticità in pazienti pediatrici deambulanti con paralisi cerebrale, di età ≥2 anni;
disabilità della mano o del polso dovuta a ictus;
blefarospasmo;
emispasmo facciale e distonie focali associate;
torcicollo spasmodico;
trattamento delle rughe glabellari e delle rughe perioculari;
iperidrosi primaria persistente e severa delle ascelle che interferisce con le normali attività quotidiane ed è resistente al trattamento topico;

The BoNT-A is approved in Italy for the following indications:
focal spasticity;
dynamic clubfoot deformity due to spasticity in ambulatory pediatric patients with cerebral palsy, aged ≥2 years;
hand or wrist disability due to stroke;
blepharospasm;
facial hemispasm and associated focal dystonias;
spasmodic torticollis;
treatment of glabellar lines and periocular lines;
persistent and severe primary hyperhidrosis of the axillae that interferes with normal daily activities and is resistant to topical treatment;

Botox was first used to treat human disease in 1968 by doctors Alan Scott and Edward Schantz.
In the 1960s, Dr. Scott, an ophthalmologist at the Smith-Kettlewell Eye Research Institute in San Francisco, began investigating new substances to be injected into the overactive muscles involved in strabismus as an alternative to conventional surgery.
His intention is to find a substance that can block neurotransmission and reduce muscle activity. Although several solutions are tested in monkeys with surgically induced strabismus, Dr. Scott does not find any successful results, until he approaches Dr. Schantz and his studies on botulinum toxin.
In 1978, Dr. Scott was given permission by the FDA to inject botulinum toxin to treat strabismus in human volunteers.
To date, the therapeutic indications for botulinum toxin A and its use in ophthalmology include: blepharospasm, strabismus and other extraocular muscle hyperactivity conditions. Doses are typically less than 30 U.

While ophthalmologists around the world begin injecting botulinum toxin into the small eye muscles for strabismus, other specialists and surgeons begin their own investigations into the use of botulinum toxin in humans.
Neurologists recognize that injections of botulinum toxin can be effective in even the largest muscle groups, to block the neurochemistry of involuntary muscle contraction.
In the 1980s, botulinum toxin was used to correct tremors and spasms of the face, eyelids, trunk and limbs. In 1989, the FDA approved treatment with botulinum toxin A for involuntary muscle contractions, strabismus, blepharospasm, and hemifacial spasm.
Today, botulinum toxins A and B are also used off-label in neurology to treat torticollis, nearly all forms of dystonia, spasticity, tremors, vocal disturbances, infantile cerebral palsy, gastrointestinal disorders, tension and migraine, and pain syndromes.
Doses up to 300 U can be used, depending on the size of the muscle groups and the area being treated.

Since the 1990s, Botox has become well known to the public as a cosmetic enhancement tool.
The history of its use in dermatology is familiar to many Canadians. In 1987, ophthalmologist Jean Carruthers observed that his patients’ expression lines disappeared after the use of botulinum toxin A for blepharospasm.
Dr Carruthers shares her observations with her husband, Dr Alastair Carruthers, a dermatologist. Together, the Carruthers discover a cosmetic treatment that revolutionizes the field of aesthetic medicine procedures.
Since 1992, the Canadian couple has been promoting the use of Botox through educational and training campaigns.
In 1996, they publish the first paper on the use of Botox for cosmetic purposes,22 and another Columbia University team also observes similar applications, although their results are published later.
Today, botulinum toxin is used in dermatology for the treatment of vertical glabellar frown and horizontal forehead lines, actinic damage wrinkles, lateral canthal lines (crow’s feet), nasal flaring, eyebrow elevation or shaping, facial asymmetry, of the upper lip and dimples on the chin.
Some reports from the mid-1990s also described Botox as highly effective for hyperhidrosis of the armpits, palms, and soles, and as a useful add-on drug combined with laser resurfacing for other cosmetic procedures. Doses range from 3 U for small facial muscles and up to 300 U for treating larger areas, such as those of hyperhidrosis.

ADVERSE REACTIONS and CONTRAINDICATIONS

The onset of any complications is always and in any case a transitory and completely reversible event. From the analysis of the available literature, no episodes of death or serious health hazards associated with the use of botulinum toxin, nor clinically detectable permanent effects, have been found. When used appropriately, in accordance with the approved indications and recommended doses, BoNT-A results in a low incidence of complications with moderate severity.

come nausea; fatica; malessere generale; sintomi influenzali; rashes cutanei; sapore metallico in bocca; reazioni allergiche; shock anafilattico (effetto descritto di recente, ma di rarissima evenienza, è dovuto alla quota di albumina che alcuni preparati contengono e non differisce da quanto può accadere con tutti i preparati iniettabili che contengono tale proteina)(1,2).

like nausea; fatigue; general malaise; flu symptoms; skin rashes; metallic taste in the mouth; allergic reactions; anaphylactic shock (recently described effect, but of very rare occurrence, is due to the amount of albumin that some preparations contain and does not differ from what can happen with all injectable preparations that contain this protein)(1,2).

discomfort at the injection site; edema; erythema; ecchymosis (the bruise is the most frequent effect due to the entry of the needle into the dermis and the rupture of a small capillary); migraine (it is not uncommon and can start 2-3 hours after the injection and last for about 6 hours); diplopia (double vision); blepharoptosis (drooping of the eyelid or eyelid ptosis); eyebrow descent.
Palpebral ptosis represents the most frequent complication deriving from the treatment of the glabellar region with BoNT-A. However, the incidence of this effect, which can be explained by the phenomenon of local diffusion of BoNT (the toxin diffuses both to the levator palpebrae muscle and to the extrinsic muscles of the eye) is minimal. However, this complication is destined to resolve spontaneously and completely within 2-6 weeks (5). Eye pain, dry eye (can occur when the toxin affects the innervation of the lacrimal gland via the greater petrosal nerve (6); Partial lip ptosis, on the other hand, can be caused by weakening of the zygomatic major muscle following injection of botox in the periocular region (4). Saliva leakage, asymmetrical smile, difficulty in speaking, inability to whistle, flaccidity of the cheeks are the most frequent complications of botulinum treatment in this area and are represented by changes in the mouth (9) Therefore, due to the great anatomical variability between patients, treatment with botulinum toxin in the lower areas of the face requires careful individual study of the patient (7).

• Ascertained hypersensitivity to each component of the formulation (botulinum toxin, human albumin, sodium chloride).

• In cases of general muscle activity disorders (myasthenia gravis and Lambert-Eaton syndrome).

• In patients being treated with aminoglycoside antibiotics, cyclosporine

• In patients being treated with muscle relaxants, calcium channel blockers, magnesium sulphate, lincosamides, anticholinergic drugs

• In the presence of infections or inflammation at the injection site.

• Pregnant and breastfeeding.

1 – Aoki KR, Guyer B. Botulinum toxin type A and other botulinum toxin serotypes: a comparative review of biochemical and pharmacological actions. Eur J Neurol 2001;8 (Suppl 5):21–9.
2 – Mahant N, Clouston PD, Lorentz IT. The current use of botulinum toxin. J Clin Neurosci 2000;7(5):389–94.
3 – Shapiro RL, Hatheway C, Swerdlow DL. Botulism in the United States: a clinical and epidemiologic review. Ann Intern Med 1998;129(3):221–8.
4 – Schantz EJ, Johnson EA. Botulinum toxin: the story of its development for the treatment of human disease. Perspect Biol Med 1997;40(3): 317–27.
5 – Spencer JM. Botulinum toxin B: the new option in cosmetic injection. J Drugs Dermatol 2002;1(1):17–22.
6 – Callaway JE, Arezzo JC, Grethlein AJ. Botulinum toxin type B: an overview of its biochemistry and preclinical pharmacology. Semin Cutan Med Surg 2001;20(2):127–36.
7 – Setler PE. Therapeutic use of botulinum toxins: background and history. Clin J Pain 2002;18(Suppl 6):S119–24.
8 – Jankovic J, Brin MF. Botulinum toxin: historical perspective and potential new indications. Muscle Nerve Suppl 1997;6:S129–45.
9 – Erbguth FJ, Naumann M. Historical aspects of botulinum toxin: Justinus Kerner (1786-1862) and the ‘sausage poison’. Neurology 1999; 53(8):1850–3.
10 – Torrens JK. Clostridium botulinum was named because of association with ‘sausage poisoning. BMJ 1998;316(7125):151.
11 – Erbguth FJ, Naumann M. On the first systematic descriptions of botulism and botulinum toxin by Justinus Kerner (1786-1862). J Hist Neurosci 2000;9(2):218–20.
12 – Erbguth FJ. Historical note on the therapeutic use of botulinum toxin in neurological disorders. J Neurol Neurosurg Psychiat 1996;60(2):151.
13 – Gunn RA. Botulism: from van Ermengem to the present. A comment. Rev Infect Dis 1979;1(4):720–1.
14 – van Ermengem E. Classics in infectious diseases. A new anaerobic bacillus and its relation to botulism. Rev Infect Dis 1979;1(4):701–19. (Originally published as ‘Ueber einen neuen anaeroben Bacillus und seine Beziehungen zum Botulismus’ in Zeitschrift fur Hygiene und Infektionskrankheiten 1897;26:1–56.)
15 – Sotos JG. Botulinum toxin in biowarfare. JAMA 2001;285(21):2716.
16 – Lamb A. Biological weapons: the facts not the fiction. Clin Med 2001;1(6):502–4.
17 – Snipe PT, Sommer H. Studies on botulinus toxin. 3. Acid preparation of botulinus toxin. J Infect Dis 1928;43:152–60.
18 – Klein AW. Cosmetic therapy with botulinum toxin, Anecdotal memoirs. Dermatol Surg 1996;22(9):757–9.
19 – Scott AB, Rosenbaum A, Collins CC. Pharmacologic weakening of extraocular muscles. Invest Ophthalmol 1973;12(12):924–7.
20 – Binder WJ, Brin MF, Blitzer A, Pogoda JM. Botulinum toxin type A (BOTOX) for treatment of migraine. Semin Cutan Med Surg 2001;20(2):93–100.
21 – Verheyden J, Blitzer A, Brin MF. Other noncosmetic uses of BOTOX. Semin Cutan Med Surg 2001;20(2):121–6.
22 – Carruthers A, Kiene K, Carruthers J. Botulinum A exotoxin use in clinical dermatology. J Am Acad Dermatol 1996;34(5 Pt 1):788–97.
23 – Carruthers A, Carruthers J. History of the cosmetic use of Botulinum A exotoxin. Dermatol Surg 1998;24(11):1168–70.
24 – Klein AW, Glogau RG. Botulinum toxin: beyond cosmesis. Arch Dermatol 2000;136(4):539–41.
25 – Carruthers J, Carruthers A. The adjunctive usage of botulinum toxin. Dermatol Surg 1998;24(11):1244–7.
26 – Carruthers A, Carruthers J. Clinical indications and injection technique for the cosmetic use of botulinum A exotoxin. Dermatol Surg 1998;24(11):1189–94.

1 – Aoki KR, Guyer B. Botulinum toxin type A and other botulinum toxin serotypes: a comparative review of biochemical and pharmacological actions. Eur J Neurol 2001;8 (Suppl 5):21–9.
2 – Mahant N, Clouston PD, Lorentz IT. The current use of botulinum toxin. J Clin Neurosci 2000;7(5):389–94.
3 – Shapiro RL, Hatheway C, Swerdlow DL. Botulism in the United States: a clinical and epidemiologic review. Ann Intern Med 1998;129(3):221–8.
4 – Schantz EJ, Johnson EA. Botulinum toxin: the story of its development for the treatment of human disease. Perspect Biol Med 1997;40(3): 317–27.
5 – Spencer JM. Botulinum toxin B: the new option in cosmetic injection. J Drugs Dermatol 2002;1(1):17–22.
6 – Callaway JE, Arezzo JC, Grethlein AJ. Botulinum toxin type B: an overview of its biochemistry and preclinical pharmacology. Semin Cutan Med Surg 2001;20(2):127–36.
7 – Setler PE. Therapeutic use of botulinum toxins: background and history. Clin J Pain 2002;18(Suppl 6):S119–24.
8 – Jankovic J, Brin MF. Botulinum toxin: historical perspective and potential new indications. Muscle Nerve Suppl 1997;6:S129–45.
9 – Erbguth FJ, Naumann M. Historical aspects of botulinum toxin: Justinus Kerner (1786-1862) and the ‘sausage poison’. Neurology 1999; 53(8):1850–3.
10 – Torrens JK. Clostridium botulinum was named because of association with ‘sausage poisoning. BMJ 1998;316(7125):151.
11 – Erbguth FJ, Naumann M. On the first systematic descriptions of botulism and botulinum toxin by Justinus Kerner (1786-1862). J Hist Neurosci 2000;9(2):218–20.
12 – Erbguth FJ. Historical note on the therapeutic use of botulinum toxin in neurological disorders. J Neurol Neurosurg Psychiat 1996;60(2):151.
13 – Gunn RA. Botulism: from van Ermengem to the present. A comment. Rev Infect Dis 1979;1(4):720–1.
14 – van Ermengem E. Classics in infectious diseases. A new anaerobic bacillus and its relation to botulism. Rev Infect Dis 1979;1(4):701–19. (Originally published as ‘Ueber einen neuen anaeroben Bacillus und seine Beziehungen zum Botulismus’ in Zeitschrift fur Hygiene und Infektionskrankheiten 1897;26:1–56.)
15 – Sotos JG. Botulinum toxin in biowarfare. JAMA 2001;285(21):2716.
16 – Lamb A. Biological weapons: the facts not the fiction. Clin Med 2001;1(6):502–4.
17 – Snipe PT, Sommer H. Studies on botulinus toxin. 3. Acid preparation of botulinus toxin. J Infect Dis 1928;43:152–60.
18 – Klein AW. Cosmetic therapy with botulinum toxin, Anecdotal memoirs. Dermatol Surg 1996;22(9):757–9.
19 – Scott AB, Rosenbaum A, Collins CC. Pharmacologic weakening of extraocular muscles. Invest Ophthalmol 1973;12(12):924–7.
20 – Binder WJ, Brin MF, Blitzer A, Pogoda JM. Botulinum toxin type A (BOTOX) for treatment of migraine. Semin Cutan Med Surg 2001;20(2):93–100.
21 – Verheyden J, Blitzer A, Brin MF. Other noncosmetic uses of BOTOX. Semin Cutan Med Surg 2001;20(2):121–6.
22 – Carruthers A, Kiene K, Carruthers J. Botulinum A exotoxin use in clinical dermatology. J Am Acad Dermatol 1996;34(5 Pt 1):788–97.
23 – Carruthers A, Carruthers J. History of the cosmetic use of Botulinum A exotoxin. Dermatol Surg 1998;24(11):1168–70.
24 – Klein AW, Glogau RG. Botulinum toxin: beyond cosmesis. Arch Dermatol 2000;136(4):539–41.
25 – Carruthers J, Carruthers A. The adjunctive usage of botulinum toxin. Dermatol Surg 1998;24(11):1244–7.
26 – Carruthers A, Carruthers J. Clinical indications and injection technique for the cosmetic use of botulinum A exotoxin. Dermatol Surg 1998;24(11):1189–94.

BIBLIOGRAFIA

1 – Aoki KR, Guyer B. Botulinum toxin type A and other botulinum toxin serotypes: a comparative review of biochemical and pharmacological actions. Eur J Neurol 2001;8 (Suppl 5):21–9.
2 – Mahant N, Clouston PD, Lorentz IT. The current use of botulinum toxin. J Clin Neurosci 2000;7(5):389–94.
3 – Shapiro RL, Hatheway C, Swerdlow DL. Botulism in the United States: a clinical and epidemiologic review. Ann Intern Med 1998;129(3):221–8.
4 – Schantz EJ, Johnson EA. Botulinum toxin: the story of its development for the treatment of human disease. Perspect Biol Med 1997;40(3): 317–27.
5 – Spencer JM. Botulinum toxin B: the new option in cosmetic injection. J Drugs Dermatol 2002;1(1):17–22.
6 – Callaway JE, Arezzo JC, Grethlein AJ. Botulinum toxin type B: an overview of its biochemistry and preclinical pharmacology. Semin Cutan Med Surg 2001;20(2):127–36.
7 – Setler PE. Therapeutic use of botulinum toxins: background and history. Clin J Pain 2002;18(Suppl 6):S119–24.
8 – Jankovic J, Brin MF. Botulinum toxin: historical perspective and potential new indications. Muscle Nerve Suppl 1997;6:S129–45.
9 – Erbguth FJ, Naumann M. Historical aspects of botulinum toxin: Justinus Kerner (1786-1862) and the ‘sausage poison’. Neurology 1999; 53(8):1850–3.
10 – Torrens JK. Clostridium botulinum was named because of association with ‘sausage poisoning. BMJ 1998;316(7125):151.
11 – Erbguth FJ, Naumann M. On the first systematic descriptions of botulism and botulinum toxin by Justinus Kerner (1786-1862). J Hist Neurosci 2000;9(2):218–20.
12 – Erbguth FJ. Historical note on the therapeutic use of botulinum toxin in neurological disorders. J Neurol Neurosurg Psychiat 1996;60(2):151.
13 – Gunn RA. Botulism: from van Ermengem to the present. A comment. Rev Infect Dis 1979;1(4):720–1.
14 – van Ermengem E. Classics in infectious diseases. A new anaerobic bacillus and its relation to botulism. Rev Infect Dis 1979;1(4):701–19. (Originally published as ‘Ueber einen neuen anaeroben Bacillus und seine Beziehungen zum Botulismus’ in Zeitschrift fur Hygiene und Infektionskrankheiten 1897;26:1–56.)
15 – Sotos JG. Botulinum toxin in biowarfare. JAMA 2001;285(21):2716.
16 – Lamb A. Biological weapons: the facts not the fiction. Clin Med 2001;1(6):502–4.
17 – Snipe PT, Sommer H. Studies on botulinus toxin. 3. Acid preparation of botulinus toxin. J Infect Dis 1928;43:152–60.
18 – Klein AW. Cosmetic therapy with botulinum toxin, Anecdotal memoirs. Dermatol Surg 1996;22(9):757–9.
19 – Scott AB, Rosenbaum A, Collins CC. Pharmacologic weakening of extraocular muscles. Invest Ophthalmol 1973;12(12):924–7.
20 – Binder WJ, Brin MF, Blitzer A, Pogoda JM. Botulinum toxin type A (BOTOX) for treatment of migraine. Semin Cutan Med Surg 2001;20(2):93–100.
21 – Verheyden J, Blitzer A, Brin MF. Other noncosmetic uses of BOTOX. Semin Cutan Med Surg 2001;20(2):121–6.
22 – Carruthers A, Kiene K, Carruthers J. Botulinum A exotoxin use in clinical dermatology. J Am Acad Dermatol 1996;34(5 Pt 1):788–97.
23 – Carruthers A, Carruthers J. History of the cosmetic use of Botulinum A exotoxin. Dermatol Surg 1998;24(11):1168–70.
24 – Klein AW, Glogau RG. Botulinum toxin: beyond cosmesis. Arch Dermatol 2000;136(4):539–41.
25 – Carruthers J, Carruthers A. The adjunctive usage of botulinum toxin. Dermatol Surg 1998;24(11):1244–7.
26 – Carruthers A, Carruthers J. Clinical indications and injection technique for the cosmetic use of botulinum A exotoxin. Dermatol Surg 1998;24(11):1189–94.